What is the ruling on storing rice, a common practice in Egyptian villages?

If merchants buy goods when prices are low to sell them when prices are high, with the intention of making a profit, there is no harm in that. This is not the prohibited hoarding, unless they buy at a time when people are in need, thereby causing hardship for them.

As for families storing their year's provisions until the harvest of the following year, there is no harm in it, and it does not contradict reliance on Allah (Tawakkul). This is based on the hadith of Umar (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) "USED TO SELL THE DATE PALMS OF BANU AL-NADIR AND RETAIN FOR HIS FAMILY THEIR PROVISIONS FOR A YEAR." It is permissible to store provisions for one's family even if the one storing them is a partner in it, contrary to those who absolutely forbid storing provisions. There is a difference of opinion regarding the permissibility of storing provisions for one who buys them from the market, but it is not permissible to store provisions at all in times of scarcity.

And Allah knows best.